Please stay away from using conduit and switch to accesslist for consistency and best practice.

"Sun Remote Procedure Call (RPC) is used by many services, for example, Network File System (NFS) and Network Information Service (NIS).

Sun RPC services can run on any port on the system. When a client attempts to access an RPC service on a server, it must find out which port that service is running on. It does this by querying the portmapper process on the well-known port of 111.

The client sends the RPC program number of the service, and gets back the port number. From this point on, the client program sends its RPC queries to that new port."

so you need to open a reverse port as well to enable communication. Best recommendation is use application protocol inspection for that interface connecting the server